Propeller and anti-icer therefor



Jan. 22,1946. R. SQJ HNSON 2,39 ,472,

PROPELLER AND ANT I I GER THEREFOR Filed Nov. 1 5, 1939' m, )2 1IINVENTOR. 1 flap/45 day/v50 Patented Jan. 22, 1946 PBOPELLER ANDANTI-ICED THEREFOR Ralph S. Johnson, West Los Angeles, Calif" alsignorto The Firestone Tire & Rubber Company, Akr n. Ohio, a corporation ofOhio Application November 13, 1939. Serial No. 304,085

14 Claims. (01. 244-134) My invention relates to propellers and hasparticular reference to airplane propeller constructions and means forpreventing the accumulation of ice and ice particles thereon.

In the operation of airplanes oneof the more serious dangers encounteredis that of flying in icing conditions due to the accumulation of iceupon the plane. Heretofore it has been considered that the ill eflectswere produced by the accumulation of ice upon the wings of the plane andthus injuring or destroying the emicency of the air foil of the wings.However, more recent investigations tend to show that it is the loss ofefllciency in the propeller air foil which causes the greatest damage byreason of the fact that a relatively small accumulation of ice upon thepropeller blade, and particularly upon the leading edge thereof,effectively reduces the efficiency of the airplane in greater proportionthan a corresponding accumulation of ice upon the wings.

As will be understood by those skilled in this art. the contour of thepropeller blade is carefully calculated and carefully constructed so asto produce the most efllcient air foil. Hence even minute accumulationsof ice upon the propeller edge surface of the propeller blade betweensuch mid point and the hub.

Another object of my invention is to provide apropeller constructionwherein conduits are provided along the leading edge of the propellerblade for conveying anti-icing liquid therealong and to provide a systemof distribution of said liquid along the propeller.

Another object of my invention is to provide one or more groovesdisposed along the leading edge of the propeller blade, such groovesbeing formed either in the body material of the propeller blade or insuitable material applied to and mechanically bonded to the body of thepropeller blade. 4

. Another object of my invention is to provide an airplane propellerconstruction in which the propellerblade is formed of a body portion ofsuitable material and is provided with a surface layer of materialmachined or ground to the desired air foil contour, and in which thesurface layer of material is so mechanically bonded to the. body of thepropeller blade that dents. scratches or cracks in the surface layer areprevented from extending into the body material blade materially detractfrom the emeiency of the blade, even the grinding out of dents orscratches suffered by the blade during normal service injuring theefficiency of the carefully designed air foil.

It is therefore an object of m invention to provide a propellerconstruction in which the air foil surface can be maintainedsatisfactorily true to its original design.

Another object of my invention is to provide a propeller construction inwhich the accumulation of ice is eflectively prevented.

Another object of my invention is to provide a method by whichanti-icing fluid may be dis-, tributed over a relatively large portionof the area of the propeller to prevent the accumulations of icethereon.

Another object of my invention is to provide a of the blade.

Another object of m invention is to provide a construction of propellerblade as set forth in the preceding paragraph wherein the surface layermaterial may be built up after being dented, scratched orcracked and bere-machined or reground to restore the original contour to the propellerblade after miury.

Other objects and advantages of my invention will be apparent from astudy of the following specifications, read in connection with theaccompanying drawing, wherein Fig. 1 is a perspective view of apropeller hub and blades constructed in accordance with my invention;

Fig. 2 is an enlarged detail perspective view of one of the blades ofthe propeller shown in Fig. 1;

method by which such anti-icing liquid can be conveyed along the leadingedge of. the propeller.

and be distributed over the leading edge thereof in such manner as toeffectively prevent the accumulation ofv ice upon the same at relativelygreat distances from the propeller. hub.

Another object of my invention is to provide a means for conveyinganti-icing liquid to the propeller blades and along the propeller bladesto a position not less than substantially midway of the length of theblade and to substantially evenly distribute such liquid over theleading Fig. 3 is a detail perspective view of a similar blade butillustrating a modified arrangement of anti-icing-liquid conduitsthereon:

Fig. 4 is a fragmentary view of the propeller shown in Fig. l andillustrating the manner in which anti-icing liquid may be conveyed tothe propeller;

Fig. 5 is a detail sectional view taken along line V-V of Fig.4 andillustrating one manner in which the anti-icing liquid may beaccumulated upon the propeller blade; 1

'Fig. 6 is a fragmentary cross sectional view through a portion of thepropeller blade shown in Fig. 1 and illustrating the grooves'or conduitsformed therein; and v Fig. 7 is a detail fragmentary view similar toFig. 6 and illustrating a modified manner in which the grooves orconduits may be applied to the propeller blade.

Referring to the drawing, I have illustrated in Fig. 1 a conventionaltwo-bladed propeller having a hub i to which the power shaft 2 of anengine may be coupled and having a pair of oppositely disposed blades 3and l secured thereto.

As is understood by those skilled in this art, each of the propellerblades 3-4 is carefully shaped to provide the most effective andeflicient air foil as it is whirled through the air, having a reasonablybroad leading edge 5 and a feathered trailing edge 5.

In prior attempts to prevent the accumulation of ice upon the propellerblades with the resultant decrease in the efficiency of the carefullyshaped air foil structure thereof, it has been proposed to depositanti-icing liquid such as alcohol upon the whirling propeller blades.However, the point of application of such anti-icing liquid has been atthe cylindrical portion of the propeller blade immediately adjacent thehub, with the result that the air forces and centriiugai force set u bythe whirling propeller have immediately thrown such liquid of! of thepropeller before there has been any opportunity to obtain a reasonabledistribution of such liquid along the length of the propeller. Theformation or accumulation of ice upon the propeller immediately adjacentthe hub does not injure or destroy the effective shape of the air foilstructure of the propeller to any appreciable extent, but even theminute ice formation which occurs upon the leading edge of the propellerso alters the attack surface of the propeller as to cause turbulence ofthe air and efiectively destroying the effioiency of the propeller.

I provide means upon each bladeof the propeller for receiving suchanti-icing-liquid and for conveying the same along the propeller towardthe tip thereof so that the anti-icing-liquid not only covers thepropeller area immediately adjacent the hub but may be substantiallyuniformly distributed throughout the greater portion of the length ofthe propeller blade. I

This means may comprise any form of conduits which may receive theanti-icing-liquid and conduct the same to a plurality of points spacedalong the length of the propeller blade; for example, as illustratedparticularly herein, such conduits may comprise a plurality ofrelatively narrow and relatively shallow grooves 1 extendinglongitudinally along the leading edge of the propeller from a pointimmediately adjacent the hub to one or more points spaced toward the tipend thereof; or the conduits may be formed as small bores (see is: inFig. 7) near the hub but which open into grooves as they extend towardthe tip of the blade.

The grooves Or channels 1, as illustrated in Figs. 1, 2 and 6, may beformed directly in the material of the blade proper as by cutting orscoring the surface of the body material of the blade and will be heldtherein by the air pressure exerted upon the leading edge of thepropeller. The centrifugal force set up by the rapidl rotating propellerwill tend to move such liquid along the length of the grooves toward thetip of the propeller, portions of such liquid spilling over from thevarious grooves as the grooves converge toward and intersect each otherso that a substantially even distribution of the anti-icing-liquid willoccur throughout the length of that portion of the propeller-which isprovided with the grooves and such liquid as will be spilled out, orthat finds way under the ice deposit, will effectively prevent theaccumulation of ice upon. the leading edge.

While one or more of the grooves may extend throughout the full lengthof the propeller blade, I y

do not believe that it is necessary or desirable to extend the same morethan somewhere between the mid point and three-quarters of the length ofthe blade from the hub since the centrifugal forces set up by therapidly rotating blade will effectively throw of! any ice which tends toaccumulate on the outermost portion of the length of the propellerblade.

The anti-icing-liquid may be supplied to or sprayed upon the groovedsurface of the propeller by a distribution system which may include asuitable supply pipe 8 from a source of liquid or a pump therefor, whichsupply pipe empties readily into an internal annular channel 9 formedupon the hub I, from which channel the liquid will be thrown bycentrifugal force through a pair of conveying pipes l0 and H, one foreach blade of the propeller, the conveying pipes having their outer endsturned inwardly toward the leading edge of the associated blades so asto cause the liquid passing therethrough to be ejected in a directionnormal to the adjacent surface of the propeller blade. While the liquiddeposited upon 0 the propeller blades may be effectively received inand, as shown in Figs. 1 and 2, one of such grooves la may extend to apoint approximately midway or beyond the length of the propeller whilethe remaining grooves may act as conducting chanthe mere ends of thegrooves I, I prefer to form a sump l2 on the surface of the bladesimmediately adjacent the hub and allow the inner ends of the grooves toextend into such sump. Such sump may be merely a depression in thepropeller surface though, as illustrated particularly in Fig. 5, Iprefer that the outer edge l3 of such sump shall extend somewhat underan overhanging ledge H which will further assist in holding liquid in.the sump ready for passage outwardly through the grooves 1.

In Fig. 3 I have illustrated a modified arrangement of the conveyinggrooves I, in which the grooves la extend in the same manner asdescribed with reference to Figs. 1 and 2 but the remaining groovesdesignated as lb are not only considerably shorter in length than thegroove in but terminate at different distances away from the hub withoutintersecting the grooves 1a; Thus each of these grooves will serve toconvey a portion of the anti-icing liquid over a desired length of theblade and insure by their arrangement a uniform distribution oftheliquid over the surface area of the propeller.

As hereinbefore stated, the grooves I and the sump I2 may be formeddirectly into the surface of the material of the propeller bladesthemselves, particularly when the material of the propeller blades iswood. When the propeller blades are formed of metal or other material,the strength of which might be weakened by scratches, scoring or groovesformed in the surface of such material, the conveying grooves and sumpmay be formed in a surface material which is applied to and.mechanically bonded to the material of the blade the .general shape andcontour of the desired propeller air foil, a layer of metallic surfacematerial extending over the surface of said blade from the hub endthereof, said surface material being mechanically bonded to said bladethroughout the area of the blade covered thereby, and

one or more grooves formed in .the surface of as distinguished from afusion or molecular intermingling of the materials so as to produce aJunction of the materials to which cracks or imperfectiong in thesurface material may extend but will be prevented from penetrating pastthe junction and into the material of the blade proper. However, a mosteffective manner of providing said layer materlal'and extendinglongitudinally along said blade to convey anti-icing-liquid along saidblade.

3. In an airplane propeller construction, a propeller blade comprising apropeller bodyhaving the general shape and contour of the desiredpropeller air foil, one or more conduits formed material into which thegrooves and sump may be formed is that of metal spraying a suitablesurface material upon the leading edge of the propeller blade to a depthsufficient to accommodate the cutting or forming of the grooves and sumptherein, such structure being illustrated particularly in Figs. 5 and '1wherein a suitable thickness of surface material It has been apof saidpropeller body and communicating with in the leading edge of saidpropeller body to convey anti-'icing-liquid along said blade, and aliquid receiving receptacle formed in the hub end the hub end of saidconduits.

4. In an airplane propeller construction, a propeller blade, a layer ofmetallic surface material plied to the body material It. Such metalspray process provides a mechanical bond between the surface materialand the body material sufllcient to maintain the surface material inplace upon the propeller blade during service.

Another distinct advantage which may be accomplished by the employmentof surface material added to the body material of the blade lies in thefact that any cracks which may occur in the surface material which haveenlarged under stresswill extend only tothe mechanical bond between thesurface material and bodymaterial and there stop. Thus the surfacematerial may be applied not only to the leading edge of the propellerblade for a distance sumcient to accommodate the groove 1 but may alsobe employed over the entire surface of the propeller blade. Thus anydents, scratches or cracks which may occur in the surface-of the bladedue to injury to the propeller while in service may be readily groundout and the propeller restored to its initial carefully calculated andformed air foil contour by rebuilding the surface material to a desireddepth and refinishing this surface t the exact desired contour.

It will therefore be-observed that I have provided a propellerconstruction which is particularly adapted for the maintenance of itscarefully designed efllcient air foil characteristics regardless ofminor injuries which may occur during the active life of the blade andregardless of icing conditions through which the plane so equipped maybe required to fly.

While I have shown and described the preferred embodiment of myinvention, I do not desire to upon at least the leading edge of saidpropeller,

and a plurality of grooves formed in said layermaterial and extendingdifferent distances longitudinally along said blade from the hub endthereof, for distributinganti-icing-liquid along saidblade.

5. In an airplane propeller construction, a propeller blade comprising apropeller body having the general shape and contour ofthe desiredpropeller air foil, a layer of surface material upon j at least theleadingedge of said propeller, and a.

plurality of grooves formed in said layer material and extendingdifferent distances longitudinally along said blade from the hubendthereof, the outer end portions of at least some of said groovesconverging toward and joining each other.

6. In a propeller construction, a blade having a i desired air foilcontour, and a plurality of antiicing-liquid conduits formed in andextending longitudinally of said blade per se and terminating,atdifferent distances along the leading edge of said blade fordistributing anti-icing liquid along said blade.

'7. In a propeller construction, a blade having a desired air foilcontour, and a plurality of antiicing-liquid conduits formed in andextending longitudinally of said blade and tennlnating at differentdistances along. the leading edge of said blade :by joining with alonger one of said conduits, 1

8. In a propeller construction, a blade having a desired air foilcontour, and a plurality of anti-icing-liquid conduits formed in andextending longitudinally of said blade per se along the leading edge ofsaid blade for distributing antibe limited to any of the details ofconstruction 4 shown or described herein, except as defined in theappended claims.

I claim:

1. In an airplane propeller construction, a propeller blade comprising apropeller body having the general shape and contour of the desiredpropeller air foil, a layer of metallic surface material extending overthe surface of said bladefrom the hub end thereof, said surface materialbeing mechanically bonded to said blade throughicing liquid along saidblade.

9. In a propeller construction, a propeller blade comprising a bladebody having a desired air foil contour, a layer of surface materialassociated with said blade body and having formed therein a plurality ofanti-icing-liquid conduits extending longitudinally of said blade, saidconduits having their radially outer end portions converging and Joiningone another. I

10. In a propeller construction, a blade having 1| said blade, the'outerend portions of at least so being provided with an anti-icing-liquidgroove extending longitudinally of said blade body from the hub endthereof for distributin anti-icingliquid along said blade.

13. In a propeller construction, a blade having a desired air foilcontour, and a plurality of antiicing-liquid grooves formed in thesurface of said blade and extending longitudinally in the outer surfaceof said blade for distributing anti-icingliquid along said blade.

14. In a propeller construction, a propeller having a hub, a deicer shoesecured to the leading edge of said propeller, a deicer liquid supplyrecess formed in the hub end of said shoe, con- 10 verging groovesformed in the weather-exposed side of said shoe, said grooves beinginter=connected and communicating with said recess. whereby deicerliquid received in said recess will enter said grooves. when saidpropeller is rotated in service, and flow therein, thus providing areason said propeller on which ice will not form.

RALPH S. JOHNSON.

